Si′mul‐ta″ne‐ous (?), a. [LL. simultim at the same time, fr. L. simul. See Simulate.] Existing, happening, or done, at the same time; as, simultaneous events. — Si′mul‐ta″ne‐ous‐ly, adv. — Si′mul‐ta″ne‐ous‐ness, n.
Simultaneous equations(Alg.), two or more equations in which the values of the unknown quantities entering them are the same at the same time in both or in all.